During the past few decades, water has become increasingly important to our modern lifestyles, especially, for relaxation and social gatherings in pools and hot tubs. More and more people build their own swimming pools inside of their homes or in their gardens and stay healthy by training their bodies in water regularly. Although water is available in many places across our planet, a reliable supply of clean water is less easy to obtain.
During the last decade, the hot tub was presented on the market as a healthy and relaxing bath, to reduce stress and relax in warm water of ca. 100° F. In these easy-to-install hot tubs, jets are installed to pump the water under high pressure within the bath, where the water power relaxes the muscles. Also, a hot tub bath has been shown to be healthy and decrease blood pressure. Taking a bath in a hot tub also became a social affair—a place where everyone can enjoy the warm water and relax after a hard day's work. This is the same with swimming pools, although swimming pools are used more for sport and conditioning. However, for a pool outside, good weather is required as well as a lot of space.
Especially in pools and hot tubs, where the water temperature is relatively high, are risky environments for rapid bacterial growth. That is why treatment of hot tub water is needed. Presently, vast quantities of chlorine are used in combination with specific bacteria-killing equipment, like ozonators or UV-C lighting. This is due to the fact that chlorine kills and removes sessile bacterial slime layers from the walls, whereas ozone or UV-C kills plankton-like bacteria. Chlorine only kills bacteria suspended in the water along with the top of the slime layers of surfaces, but not all microorganisms since many microorganisms grow within the slime layer.
However, the disadvantages of chlorine are:    1. It has an unpleasant odor    2. It irritates the skin, and dries it    3. Many people are allergic to chlorine and their eyes become irritated if they come into contact with the chemical    4. Chlorine not only eliminates water-born bacteria but also destroys benevolent dermatological bacteria    5. Breathing directly above the water surface is irritating to the lungs    6. After a bath, people have to take a shower to eliminate chlorine residue    7. Chlorine is not environmentally friendly    8. People generally have to wash and/or treat their skin after a bath.
When water is treated with chlorine, it is necessary to keep the pH value between 7.2 and 7.8, because higher or lower pH values reduces chlorine efficiency. However there is no reason why water should not have a pH of around 8.2 like seawater of which the medical qualities are well-known.
In order to maintain the pH in chlorine treatment between the optimal values, it is necessary to dose pH+ or pH− additives. In practice, this means that the owner of a hot tub or pool is always measuring pH values to keep the water in good condition. Technically it is possible to control this by means of a computer, however the instruments are expensive. Besides chlorine, there are other methods for treating water, such as bromide. In combination with chlorine, it forms bromine. In most countries the use of bromide is forbidden due to suspected carcinogenic action by the formed bromate.
Up to now there is no solution for water treatment that will not irritate the skin or cause skin damage. Furthermore, there is an urgent need for water treatment additives that are environmentally friendly, healthy, gentle on the skin, that do not irritate the airways or the eyes.